1. Field of the Invention
The present invention relates to an image forming apparatus, such as a copying machine, for forming both an original image of an original document and an additional image comprising, for example, the time and date of copying, the author of the original document or a distribution list. More particularly, the present invention relates to an image forming apparatus in which copies of original documents may be produced having additional, operator selected information included thereon.
2. Description of the Related Art
Today, copying machines are standard office equipment and can efficiently copy large numbers of documents in a short time period. Effective organization and management is therefore necessary to handle the copies which are produced. Often, the copies are to be distributed throughout the office in accordance with a distribution list. The copies may, for example, be an excerpt or article from a book or magazine. It is desirable in this instance to provide an indication of the source of the article. It may also be desirable to note the time and date of copying in order to quickly identify later versions of documents, etc. In many instances, these notations and other additional information are handwritten, stamped, or typed on the copies. However, these procedures are time consuming and require the attention of one or more persons.
Electronic copying devices have recently been developed in which such additional information, including, for example, alphanumeric characters, may be formed on paper utilized as the recording medium. In one such device, recording paper having an original image of an original document is transported to an image forming section. An additional image of the additional information, such as alphanumeric characters, is then formed on the recording paper having the original image formed thereon. Thus, two steps are required for the complete image formation, i.e., the step of forming an original image and the step of forming an additional image. Accordingly, the image forming speed of such a copying machine is slower than the corresponding image forming speed of conventional one-step original image formation. Additionally, it is difficult to precisely position the additional image on the recording medium.
Another copying device which permits additional information to be formed uses a shutter, solenoid and spring to form the additional image on a photosensitive drum. This device, however, suffers from the disadvantage of having slow shutter movement with respect to the rotational movement of the image forming photosensitive drum. Consequently, the additional image produced will be larger than necessary and may interfere with the full and complete reproduction of the document being copied.
Commonly owned, application Ser. No. 337,738 filed Apr. 13, 1989, discloses an image forming apparatus for forming an original image and an additional image. That apparatus, however, uses a light emitting diode array. Such arrays have a slow operation time in forming the additional images.
Another type of copying machine has been developed in which an original image is read from an original document and the image data is then converted into an electrical signal. The original image is reproduced using the electrical signal. This type of copying machine is known as a digital copying machine. With digital copying machines such as, for example, laser printers, the additional image can be written on the recording paper while the original image is being copied. However, digital copying machines are more expensive than conventional electronic copying machines.